PROVIDED. Systemic lupus erythematosus (SLE) is an autoimmune disease with significant morbidity due to end organ damage mediated by autoantibodies that target nucleic acid-containing immune complexes, along with inflammatory cells and their products. While important observations related to immune regulation and effector mechanisms in SLE have suggested some therapeutic approaches to inhibit autoantibody production and abrogate tissue damage, it would be highly desirable to intervene at the afferent stage of SLE, when autoimmunity is developing. Unfortunately, less information is available regarding these early events. Recent data have documented prominent overexpression of mRNAs encoded by genes regulated by interferons (IFNs) in peripheral blood mononuclear cells from lupus patients. In view of the pleiotropic effects of IFNs on diverse aspects of immune function, many of which could contribute to generation of autoimmunity and inflammation, it would be of high importance to determine the upstream triggers and intracellular pathways that account for activation of the type I IFN (IFN-a) target genes in SLE. In that regard, our data indicate a potential role for RNA in the activation of the IFN pathway in SLE patients. The proposed research will focus on an analysis of the triggers and pathways that account for the increased expression of IFN-a and its downstream target genes. The research will address the hypothesis that activation of gene expression through an RNA-dependent Toll-like receptor (TLR) pathway is an important mechanism of IFN pathway activation, and altered immune system activation, in SLE. The specific aims are: 1) To identify the TLR pathways that mediate IFN expression in SLE;2) To study the stimuli for TLR pathway activation in SLE;3) To characterize the downstream targets of TLR pathway activation in SLE;and 4) To study the response of SLE lymphocytes to IFN. Elucidation of this important pathway should lead to more targeted modulation of disease mediators in systemic autoimmune diseases.